Automatic control



May- 7, 193?.v A. E. KROGH 2,000,235

AUTOMATIC CONTROL Filed April 24, 1931 10 Sheets-Sheet 1 PRESSUREDOSTILLATE VAPOR LINE FIG I.

PRESSURE DIS LATE RECIRCUL NC- SPRAY PRESSURE DISTILLATE VANR LINE LINEHOT F T0 DE FHLE'GMATO R DEPHLEG MATO R T R i oe uuemron i 1 REACTIONCHAMBER TRANSFER LINE ACKING S LL A TTORNEYS.

May 7, 1935.

'A. a KROGH AUTOMATIC QONTROL Filed April" 24, 1931 10 Sheets-Sheet 2umarumzuh. uu zaa.

onu N ohm mung-F (has mos

I W OQ A TTORNEYS.

3n EN N NQNRN y 1935.1 A. E. KROGH 2,000,235

AUTOMATIC CONTROL Filed April 24, 1931 10 Sheets-Sheet 3 mmsrcnTEMPERATURE rummcs 'r: MPERAI'URE \7 Flam Mam Lme IN VEN TOR.

' 'A TTORNEYS.

May 7, 1935. A. E. @oGH 2.000.235

AUTOMATIC CONTROL v Filed April 24, 19:51 lO-Shee ts-Sheet 4 FIG:

rEIfro i2,

' ATTORNEYS.

May 7, 1935. A. E. KROGH AUTQMATIC CONTROL Filed April 24, 1931 l 0Sheets-Sheet 5 INVENTOR. 5721122 I Elimylz BY y m ATTORNEYS.

y 7; 1935- A. E. KROGH 2,000,235

AUTOMATIC CONTROL Filed April 24, 1931 l0 Sheets-Sheet 6 INVENTOR.flniferfiflfrayk,

A TTORNEYS.

MayJ, 1935, A. E. kRoGH 2,000,235

AUTOMATIC CONTROL Filed April 24, 1931 10 Sheets-Sheet 7 FIG? WINVENTOR. HnKerEJfiWk,

TTORNEYS.

y A. E. KROGH 2,000,235

AUTOMATIC CONTROL Filed April 24, 1931 1O Sheets-Sheet 8 INVEN TOR.

A. E. KROGH AUTOMATIC CONTROL May 7, 1935.

Filed April 24, 1931' 10 Sheet-Sheet '9 Fla 4K- y 7, '1935- A. E. KROGH0,235

AUTOMATIC CQNTRQL Filed April 24, 1931 1 l0 Sheets-Sheet 10 A TTORNEYS.

Patented May 7, 1935 UNITED STATES so'rom'rrc CONTROL Anker E. Krogh,Philadelphia, Pa., assignor to The Brown Instrument Company,Philadelphia, Pa., a corporation of Pennsylvania Application April 24,1931, Serial No. 532,668

56 Claims.

This invention relates to an automatic control system and moreparticularly to an automatic control system for operating an oilcracking unit.

The characteristics of an automatic control system are determined by theoperating characteristics of the system to be controlled. In thesimplest type of apparatus used for carrying out any kind of processing,the automatic control which is to be effected may be of one variablecondition such as temperature, pressure, speed, or the like to be heldto a predetermined schedule, and there. is one condition which may 'bead- Justed at will and which is so related to the variable to bemaintained on schedulethat by variation of the regulatable condition,the variable may be adjusted to maintain it on the predeterminedschedule. For example, the heat supply may be adJusted to maintain atemperature, or the speed of a pump may be adjusted to maintain apressure, or the steam supply may be adjusted to vary the speed of anengine. In such a simple system under control, accidental variations inthe variable quantity which it is desired to hold to the schedule, arecompensated for by 5 regulation of the single condition. Likewise,accidental variations in the status of the regulate.- ble conditionaiIect the variable quantity correspondingly and cause a readjustment ofthe regulatable condition to maintain the variation to to schedule. Insuch systems the inertia of the regulatable condition, the time lag orprocess lag existing between the variable and the regulatable condition,and the extent and rate of accidental variations of both the variableand the regulatable :5 condition, are the essential factors indetermining the design and operating characteristics of the control.system. Automatic control systems for such simple processing apparatusare well known. The problem of controlling a processing appa ratusautomatically is greatly complicated by the multiplication of either thenumber of variables to be maintained on schedule, or the number ofregulatable conditions available. In industrial processes involving morethan one of either variable condition to be held to schedule, or aregulatable condition to be adjusted, there are, in addition to thefactors which determine the design and apparatus of the control systemabove pointed out, the following factors to be taken into consideration.Where two ultimate variables are to be held to schedule there usually isa relation between ultimate variables such that accidental variations inone cause changes in the other, and such that when adjustment is madethrough a regulatable condition to bring one or the other 01' theultimate variables back to schedule, the effect of the adjustment uponboth of the ultimate variables must be considered and; attention must begiven to the inertia efiects and time lags involved between the effectthat the adjustment of a regulatable variable has on both or all of theultimate variables, and also the effect that any one of the ultimatevariables has upon the others, Furthermore, one or both of the variablesultimately to be held to schedule may, when accidentally orintentionally varied, have a corresponding effect upon a regulatablecondition, which effect upon the reg ulatable condition in turn affectsone or more of the variables ultimately to be held to schedule.

In still other cases the number of regulatable conditions which areused, may be two or more, and may affect a variable condition ultimatelyto be controlled to diiferent degrees, with different time lags, and indifierent directions, and at different rates. Also in such cases theultimate variable may, when changed, aiIect either one, or both, or allof the regulatable conditions.

In still other cases the number of variable conditions ultimately to becontrolled to schedule, and the number of regulatable conditions whichit is necessary to adjust, may both be two or more, with the attendantpossibilities of the variable conditions affecting one another andaflecting the regulatable conditions of the regulatable conditionsaffecting one another, and of various of the regulatable conditionsaffecting various of the variable conditions ultimately to be held toschedule in various combinations. It is to systems for carrying outindustrial processes involving a complex combination of variableconditions ultimately to be maintained to schedule and regulatableconditions which are interrelated casually, that this inventionpertains. In the specific form of processing apparatus which serves toillustrate this invention, two regulatable conditions and three measuredconditions are involved, there being a complex interaction between thevarious conditions measured and the regulatable conditions which takesplace in various combinations in sequence, but the invention is notlimited to a particular number of measured or regulatable conditions,nor to the particular combination and sequence of operations involved inthe particular system hereunder described.

While the invention in its broadest aspects is not limited to theparticular illustration hereunder described, yet the application of theprinciples of the invention to the particular form of processingapparatus, namely, a system for cracking oil, involves variouscombinations and arrangements specifically new and useful thatconstitute part of this invention.

The specific objects and advantages of the present' invention will bemade apparent in the following detailed description when taken inconnection with the accompanying drawings, in which Fig. 1 is adiagrammatic view of a portion of an oil cracking processing apparatushaving an automatic control system embodying the principles of thisinvention applied thereto.

Fig. 2 is a schematic view showing the manner in which the componentparts of the automatic control system are interrelated.

Fig. 3 is a view similar to Fig. 2, showing the component parts of theautomatic control system combined and operating in another way.

Figures 4, 5, 6, 7, 8, and 9 are views in perspective, top plan,elevation, and cross section of an automatic control pyrometer, whichforms one of the component parts of the automatic control system of thisinvention.

Fig. 10 is a diagrammatic view partly in section, of a liquid levelgauge, which forms another component part of the system of thisinvention.

Fig. 11 is a view in plan of a motor driven valve control unit whichforms another component part of the system herein described by way ofillustration of this invention.

Referring to Fig. 1, there is shown a furnace I designed to supply heatto tubes 2, through which oil to be cracked is passed continuously. Theheat supply is created by burning oil in Jected through passages 3 intothe combustion chamber of the furnace, the products of combustion beingconveyed away through flues l, the heat being transferred to the tubesand oil contained therein by direct contact with the gaseous products ofcombustion and also by heat radiated from the combustion chamber throughthe tubes along the top and the front walls of the furnace. The heatedoil is conveyed from the furnace through the transfer line pipe 5 andfed into the reaction chamber 6 near the'top thereof. Due to the largeincrease in temperature of the oil passing through the tubes within thefurnace, the pressure upon the oil is necessarily high so that the oilflowing into the reaction chamber is under high pressure and at a hightemperature. The reaction chamber is partially fllled with the residuefrom the previous continuous operation of the system which may be drawnoff from time totime through the draw-off lines shown. The oil underhigh pressure and at a high temperature when conducted to the reactionchamber.

expands and vaporizes, and the process of cracking takes place or iscompleted. The vapors resulting from the cracking, which compose thehydrocarbon constituents of low boiling point. are conducted from thereaction chamber through the vapor line 1, and the residue consistingmainly of those hydrocarbons which are of high boiling point, settle inliquid form in the bottom of the reaction chamber from which they may bedrawn off as conditions require.

The vapors conveyed from the reaction chamber through the vapor line Iare led into the dephlegmator tower 8 at the lower portion thereof andthe vapors flow upwardly through the dephlegmator tower bubbling throughand passing over the condensate in the trays 9 and being subjected to aspray of pressure distillate which is recirculated through the crackingsystem again. Raw, hot oil is. fed into the dephlegmator and flows overand through the trays 9. By so treating the vapors from the reactionchamber to a condensing and absorption process, a separationof the lowerboiling point fraction from the higher boiling point fraction isobtained, the vapor composed of the hydrocarbons of low boiling pointeventually finding its way out through the top of the dephlegmator andis conveyed through the pressure distillate vapor line to a suitablecondensing unit. That part of the'vapor fed to the gephlegmator towerfrom the reaction chamber,which consists of the hydrocarbons of highboiling point, is condensed and absorbed by the supply of raw hot oilcarried in the trays 9. To effect an accurate separation of thehydrocarbons of low boiling point, the temperature within thedephlegmatortower'is maintained constant, or such that the temperatureof the vapors flowing from the top of the tower is constant, by asuitable temperature regulator (not shown) measuring the temperature inquestion and adjusting either the feed through the pressure distillaterecirculating line, or the feed of raw hot oil through the dephlegmatortower.

r The mixture composed of the raw hot oil fed into the dephlegmator, andthe condensate from the vapors from the cracking process, passes to thebottom of the dephlegmator.tower and into the reflux leg. A pump Illdraws the hot oil from the reflux leg and feeds it through line H intothe tubes 2' within the furnace. Another oil feed line I! is providedfor supplying oil to the tubesI. The supply of oil to the tubes 2 may beeither in partor wholly through the line H from the dephlegmator tower.

In the operation of an oil cracking unit, such as'is partially'shown inFig. 1, the maximum 3 amount of certain'constituents; such as gasolene,are sought for. In order to obtain such an operating condition, it'isnecessary that the reaction in the reaction chamber proceed ascompletely as possible to the production of the desired hydrocarbons.The reaction is controlled chiefly by the temperature and the pressureof the oil reacting, therefore it is essential that the oil fed into thereaction chamber from the cracking still be at a "certain preedterminedtemperature. At a given temperature the pressure of the oil issubstantially constant. being dependent essentially upon thetemperature, although the pressure and composition of the oil being fedthrough the tubes is a factor and the pressure in the reaction chamberare factors affecting the pressure of the oil as it issues from thetransfer line. lie-- cordingiy, one of the variable conditions to beheld to a predetermined schedule in this particular system chosen toillustrate the invention, is.

the temperature of the oil in the tubes as it issues from the cracldngstill, and a convenient and practicable temperature measuring device isa thognocouple II inserted-in the oil line at that D I The temperatureof the oil issuing from the cracking still depends upon the amount ofheat transferred to the oil, upon the rate at which the oilis advancedthrough the tubes, and upon the heat capacity of the oil. of thoseconditions which affect the temperature of the oil issuing from thecracking still, the heat transfer to the oil and the rate of oil flow,are possible of variation. Accordingly, the supply of combustible to thefurnace is adiustable through a valvecontrolled by motor 212 whichadjusts the valve opening in the gas or oil fuel feed line to change theheat supply and therefore the heat transfer to the oil. Inasmuch as thefurnace is inherently of large thermal capacity, and the volume of oilheated is large, changes in the fuel supply produce a resulting changein heat transfer slowly, and the resulting change in heat transferslowly affects the exit oil temperature, therefore a large time lagexists between variations in fuel supply and corresponding variations inexit oil temperature; The maximum fuel supply is limited by the capacityof the furnace structure and tube structure to resist burning out. Also,the furnace itself is subject to changes which afiect the heat transfer;for instance, the changes in outside temperature from season to seasonand correspond to a certain heat transfer tcthe 611. In view of the timelag which exists betweenchanges in heat supply and changes in exit oiltemperature, the heat supply'might change greatly before the exit oiltemperature registered that change and so a wide fluctuation in'exit oiltemperature would ensue because of the large varia tion in' heat supply.In order to reach the cause of such variations in exit oil temperature,it is desirable. and practicably useful to measure the intensity 'of theheat supply, namely the combustion chamber temperature, and to'alsoadjust the valve controlled by motor 212 so as to maintain a steadycombustion chamber temperature despite/accidental variations in heatsupply.

' Theftemperature of the exit oil may also be varied and therefore heldto a predetermined schedule by adjusting the rate of supply of oilthrough the tubes, and accordingly 9. control motor 2 l is provided foradjusting the steam valve to vary the supply of steam to the pump i0,and

' therefore the rate of supply of oil through tube 'crn 1 to the tubes.

ll. However, the oil passing through conduit II is taken from the refluxleg or the bottom of the dephlegmator tower. Obviously the rate at whichthe oil is drawn from the tower must not be so great as to exhaust thereflux leg thereby causing a cessation of oil flow from that source Onthe other hand, the level of oil in the bottom of the dephlegmator towermust be kept within certain maximum limits in order that thedephlegmator may operate efficiently. The supply of oil in the bottom ofthe dephlegmator tower is affected by the rate of supply of raw hot oilinto the top of the dephlegmator, by the rate of supply of pressuredistillate from the recirculating line, by the rate of supply of thevapor from the reaction chamber, and by the proportion of condensateseparated out from the vapors entering the dephlegmator from thereaction chamber. It is apparent. therefore, that the quantity of oil inthe bottom of the dephlegmator tower is subject to accidental variationsfrom many sources. Accordingly, the rate at which oil is drawn from thebottom of the dephlegmator must be adjusted to take care of changes inlevel of the oil in the dephlegmator tower. and at the same tfme toallow for the effect of a change in oil supply to the cracking stillupon the exit oil temperature. Accordingly, a liquid level gauge I6 isconnected with the bottom of the dephlegmator tower or with the refluxleg and measures oil level therein.

The reaction by which heavy hydrocarbons are cracked to form lighterhydrocarbons depends both upon temperature and the length of time thatthe oil is maintained at the temperature in question. Accordingly,changes in heat supply to the oil in passing through the tubes 2 in thecracking still, and changes in the rate of supply of oil through thetubes of the cracking still, affect the cracking'reaction and thereforeaffect the proportion of condensate which is separated from thehydrocarbons of low boiling point in the dephlegmator tower.-

Thus it is seen that there is in-the particular processing apparatus,partially shown in Fig. l, and described as illustrating this invention,a plurality of conditions, some of which are to be held to predeterminedschedules orwithin pre determined limits, and some of which may beregulated subject tocertain operating conditions,

all of which are interdependent in variouscombinations, and in'order tocontrol automatically 'such an industrial-process it is necessary totake other in various combinations; Thus the transfer line oiltemperature depends proximately upon the heat supply to the oil passingthrough the cracking still and upon'the oil supply through the tubes ofthe cracking still, and also upon accidental variations such-as-changesin oil quality. The level 'of liquid in the bottom of the dephlegmatortower depends proximately upon the rate of oil supply from thedephlegmator to the cracking still, upon the supply of vapor from thereaction chamberto the dephlegmator tower, upon the feed of raw hot oilto the dephlegmator, upon the feed of pressure distillate from therecirculating line, upon the extent to which cracking takes place. andupon many accidental factors. In turn, the supply of vapor through thedephlegmator depends upon the transfer line temperature and rate of oilsupply through the cracking still. The proportion of condensate from thevapor passing through the dephlegmator tower depends upon thetemperature within the dephlegmator tower. The degree to which thecracking proceeds, depends upon the transfer line temperature and therate of oil supply, and the rate of heat supply. In addition, thecombustion chamber temperature, which is indicative of heat supply,depends upon the rate of fuel supply, quality of fuel supply, changes inambient conditions. and many other accidentally variable conditions. Theheat transferred to the oil depends upon the condition of the tubes andthe condition of the furnace. It is apparent, therefore, that the wholesystem is one of the interlocked and interrelating conditions, none ofwhich can be considered independent of the other for purposes-ofautomatic control. v

The temperature measuring devices, namely,

thermocouples i3 and II for measuring the exit.

oil temperature and the combustion chamber temperature respectively,operate pyrometers fl and it provided with suitable control mechanism.Liquid level gauge 16 operates a control instrument 20. i

Pyrometers l8 and iii are each provided with a galvanometer 2i actuatedby the electromotive force generated by the respective thermocouples,and provided with a pointer 22. (See Figures 4 to 9 inclusive). Thepointer 22 follows by changes of position the changes of electromotiveforce of the thermocouple and therefore changes of the temperaturesmeasured. Due to the large number of factors which affect and tend tocause variations in the measured conditions, and also variation of themeasured condition and have the capacity to effect regulating actionswhich are in accordance with the rate and direction of change of themeasured quantity. Such regulating actions of the control instruments inaccord-' ance with rate and direction of change of meas ured conditionmay, as circumstances require, be made independently of anypredetermined neutral or predetermined schedule; or, on the other hand,such control actions may be made with allowance for and in addition tocontrol action dependent upon and made in accordance with the extent ofdeparture of the measured condition from a predetermined schedule ornormal. The necessity of maintaining the exit oil temperature, forexample, to an exact predetermined schedule, makes necessary theprovision of control action by the control instruments which tendsalways to bring the measured condition back to the predeterminedschedule, and therefore must bein accordance with the direction-ofdeparture of the condition from schedule and may be inaccordance withthe extent-of that departure. Like-.

an exact point is not so important as preventing the change in levelfrom taking place too rapidly. Accordingly, the apportionment of controlaction or strength between that tending to return the measured conditionto schedule and control action made in accordance with the rate ofchange of the control condition, may be different in diil'erent cases.

In order to gauge the rate of change of measured condition, a step table23 having steps 24 arranged to engage the pointer 22, is provided. Steptable 23 is provided with apertures 25 through which shaft 25 passes,the step table being free to rotate upon the shaft 26, the shaft 28being journalled for rotation 'in the side plates 21 of the instrument.The step table 23 is provided with a tall 23 extending downwardly fromthe table and having a lip 23 engageable by a bar 33. The bar 34 haslaterally extending arms 3| provided with apertures through which theshaft 26 extends. Set screws 32 pass through the apertured ends of arms3|, securing the bar to the shaft 2 for rotation therewith. Rotation ofthe shaft 2 operates through bar 33 to turn the step table 23 around theaxis of the shaft 26 into pointer engaging position.

In order to hold the pointer'from movement when it is engaged by thestep table 23, provision is made for clamping the pointer prior to theengagement of the step table with the pointer, the clamping action beingmade adjacent the step table so as to support the pointer under the loadof the step table. For clamping the pointer there is provided adepressor bar 33 which extends across and over the path of movement ofthe pointer 22. The depressor bar is supported by arms 34 which may beintegral therewith and which are apertured as indicated at 35, throughwhich apertures a shaft 38 passes, the shaft 35 and arms 34 beingsecured together by set screws 31. Rotation of the shaft 36 effects theoscillation of the depressor bar 33 into and out of engagement with thepointer 22. When lowered, the depressor bar clamps thepointer between itand a suitable supporting surface beneath the pointer extending in linewith the depressor bar 33. Such a surface is formed by the ridge oranvil-like formation 38 in the sheet metal guide 39 which extends acrossthefront of the instrument and is supported at its ends in the sideplate 210! the instrument. e

when it is desired to make a record of the measured condition, a chart(see Fig. 10) is positioned over the sheet metalguide 33 and is advancedby a driven roller 40 provided with studs 4| for engaging in aperturesat the margins of the .chart paper, the chart paper being drawn from anysuitable source of supply and the roller 43 being operated from asuitable source of power. In such cases a ribbon, such as a typewriterribbon or a ribbon of carbon paper (not shown) is positioned beneath thepointer 22 and over the ,chart paper ,and above the ridge or anvil 33 sothat upon depression of the pointer22 by the depressor bar 33,a mark ismade at the intersection of the pointer 22 with the anvil 33, the markbeing made .upon'the paper through the ribbon. I'he operation of theinstrument as a controller is in no way dependent upon a record of theconditions measured. .v

Provision for oscillating the depressor bar periodically areas follows.The crank arm ,42 is journalled for free rotation upon shaft 35 and isprovided with a cam follower 43 which rides upon cam 44 secured uponshaft 45, journalled in the frame plate, for rotation therewith. Apinion 43 is fixed upon shaft 45 and is driven by spur gear 41 in meshtherewith. Spur gear 41 is journalled for rotation upon stud shaft 48fixed in an -end plate of the instrument. Spur gear 41 is driven bypinion 49 rigid with the shaft 53 of motor 5|. The motor may be andconveniently is a standard electric clock motor, and suitable gearing(not shown) between the shaft 50 and the armature of the motor 5| may beprovided. The continuous rotation of the motor 5| operates through thegear train 49, 41 and 46 to rotate cam 44 in a counterclockwisedirection, as viewed in Fig. 7. Rotation of the cam 44 oscillates thecrank arm 42 about shaft 36. Crank arm 42 is provided with a laterallyextending finger 52 which engages with a set screw 53 threaded in lug 54integral with arm 34 of the depressor bar. The crank arm 42 throughfinger 52 lifts the depressor bar 33 to free the pointer 22. As therotation of the cam 44 continues, the cam follower 43 falls from a highpoint to a low point on the cam 34, as shown in the various Figures 4, 7and 9, thereby permitting the depressor bar 33 to drop and clamp thepointer between it and the sheet metal guide 33. The extent of movementdownwardly of the depressor bar is limited by set screw 55 threaded intoan arm 34 of the depressor bar and engaging with the frame of themachine.

The pointer while held in position, is then an gaged by the step table23, the movement of which is efiected by rotation of bar 30 carriedrigidly by a shaft 28. In order to effect the oscillation of shaft 26and thereby the oscillation of step table 23, the shaft 26 is providedwith a rocker arm 53 that carries an adjustable weight for balancinglector lever is moved 'into active position -into a;

of the" pointer; 22 relative to the table 23; v j

The selector levers 81, 88,- and 89 are pro'vided" with'tails 18arranged to'be'engaged by finger l1 mines the selection and degree ofcontrol action about the shaft I8, theselector levers'beingjnovedlj outof "engagement with the" finger .88 atjbneendj je s se nti h t e i'is i'i s. t

wise, when the pointer 22 is engaged by one of the uppermost steps 24,as illustrated in dot and dash lines in Fig. 5, the selector finger 88is moved'into" position to an extent determined by the position offinger 88, because of the conformation ofthe' stepped projection I3,as'shown in 'dot and dash lines in Fig. 5. Thus a high, low," or neutralsedegree determined by the position extending laterally from crank 18journalled on shaft 18 (see Fig. 9). The crank I8 carries cam follower19 which rides on cam 89. 'As the cam;

59 rotates, the crank 18 is'caused tooscillate' about shaft I8 and tomove finger ,I'! to and fro; so as to oscillate selector levers 81,88,,and 89 v I ,control action whichisinprecise accordance-with thedirection and rate .of, "change of measured jeanfiitiqri, it isneee's'sagy that-the immediately of theoscillationjand beingallowedtomoiye' lnto Fig". 4 the cam follower is is shown justafter it haspassedthe high point of the 'cam.59 'and fallen into the low point .of 'thecam in which position the finger I1. is moved to its o utrnost" righthand position, allowing the selector levers 81, 68, and 89 to engage thefinger 88. Cam follower I9 falls after cam follower 58 has fallen.

The selector levers 81, 88, and 89 have lugs 88 through which pins 8|are threaded. The heads or pins 8| are arranged to thrust againstelectric contacts 82 which are in the form .of fiat .strips mounted in ablock of insulating material 83 and connected with lead wires 84. Thepins 8| project through apertures 85 in the block 83 to engage thecontacts 82. Complementary and similar contacts 88 are likewise carriedin the block 83 and connected with electrical leads8l. Contacts 82 and86 form pairs, there being a pair corresponding to each of the selectorarms- 81, 88, and 89. When the selector levers 81,88, and 69 areactuated and moved into contact with the selector finger 88, thecorres'pondingg contacts 82 are moved to the right, as shown in Fig. I,to an extent corresponding to the extent of rotation of the selectorlevers 81, 88, and 8,9. The contacts 88 are engaged by pins 88adjustably secured to the rock lever 89 journalled for oscillation aboutstud 98 secured to the side plate of the instrument. A spring 8| securedto the rock lever 89 and to a stud 92, tends to rotate the rock lever 89in a counterclockwise direction until stopped by pin 98. The rock lever89 is provided with a tongue 9| arranged to he engaged by slot in hook98. The hook 88 is rotatably secured to the end of crank 18 by pin 91and is provided with a cam surface 88 which rides over a pin 99 carriedby eccentric I88 secured to the side plate of the instrument. Pins 8Iand 88 and eccentric I 2,080,285 sition of the pointer 22 relative totable 23. Like-' Inasmuch as the direction and "extent of the I88 may beadjusted as required to'eflect proper cooperation between the relatedparts'.

When the crank 18 'is moved to its outmost right hand-position, as shownin Fig.3, the cam surface 98 of hook 98 Titles over the pin "so that theslot-95 latches with the tongue 88. Upon subsequent rotation of the cam59 and consequent oscillation of crank", thehook 88, because of itslatched engagement with tongue '98, rotates the rock lever'89 in aclockwise direction'thereby acting through pins 88 tomove contacts 88 tothe left, as shown in Fig; 7,' into fengag'einentwith that one of thecontacts 82 which has previously been adjusted into active position bymovement of one of the selector levers 81, '88, and 89,asdetermined'byjthe position of selector finger, "and ultimately by theposition fof pointer" 22 relative pointer movement'rela'tive totheitab'le 28 detereflected ,throughthej contacts'82 j aind 8 8,[it isevidentfthat rorza single'ope'rationthe jc'ontrol;.

'actionisin'accordance with the rate of change ,of the conditionmeasured; In-orderv that each.

cycle; of 'opeiationbtthe controls may effect a 'cycle'to cycleofjoperationofft he instrument, .determined the controlaction andtherefore the of the pointer when the step table engages it as a t m f te ne t, m he W tergr etion, it is necessary that the step table be ad-.jused after each action of the tablein gauging the position of ,thepointer so thatthe neutral step of the table 23 w ill occupy theposition corresponding to that occupied by the pointer when the pointerposition was last gauged by the step table. Accordingly, the step tableis arranged for adjustment laterally, as viewed in Fig. 6, that is, inthe direction of movement of the pointer 22. In order to adjust thetable 28 laterally, a U-shaped bar I8 I having its upturned endsapertured to receive the shaft 28, is positionedwith. the upturned endsin juxtaposition with-the sides of. steptable 28, asshown in Figures 4and 6. An extensionl82 connects the U-shaped bar "I, with asleeve I83through the bore of which extends a spirallygrooved shaft 184. aThesleeve' I88 carries a projection-I85 whlchrides in the spirallygrooved shaft I84.- Rotation .of spirally grooved shaft I84 causes thesleeve I88 to move laterally and thereby shifts the U-shaped bar I 8|laterally on shaft 28. The-step table 28 is free to slide along shaft 28and is carried in lateral movement with the U-shaped bar III. A

pointer I88 may be secured to the sleeve I88 for.

the" operation 10f a suitable corresponding adjustment otthe includingthe adjustable pins 8| and 83 dete ing the period of engagement of eachof the dif- -ferent contacts 82 with thecorresponding contest. When anyof the table steps 24 is horiof the step table 23. When the operativesteps 24 of the table are each of a width-practically equal to thethickness of the pointer 22 as shown in Figs. 4 and 5, the mechanism maybe, and in some cases advantageously is adjusted so that the step tablewill be moved in a direction and by an amount such as to bring theneutral step of the step table 23 into the position last occupied by thepointer 22 when it was engaged by the step table 23. The adjustment ofthe neutral step of the table into the position previously occupied bythe pointer, as'just described, requires not.

only that the difierent operative table steps should be each of ahorizontal length about equal to the thickness of the pointer, but alsorequires parts zontally elongated as are three steps shown in Fig. 6,the engagement of such a step with the pointer can produce-no adjustmentof the table which*-isselectively-dependent upon the point along thelength of the step actually engaged by the pointer. "With threehorizontally elongated steps as shown in Fig. 6, the table will beadjusted in one direction or the other for definite distancesaccordingly as the pointer is engaged by the high or low contact. Insuch case, the

actual neutral condition of the instrument permits a range of movementof the pointer along the length of the horizontally elongated centralstep 24.

The shaft I 04 carries at its left extremity (Fig. 4) a spur-gear H2which meshes with and drives spur gear H3 journalled on stud I I4secured to a side plate 21 of the instrument. The stud shaft II 4carries a disc H5 rotatable thereon, a collar being provided on theouter extremity of the stud shaft II4 to support the disc H5. Atriangularly shaped spring H6 fits about the shaft H4 and thrustsagainst the faces of the spur gear H3 and disc H5. The spring H5 acts todrive the disc I I5 from thespur gear I I3. The disc I I5 has clips H1secured thereto by screws H8, the clips being adjustable about thescrews H8 and securable in adjusted position by the screw and slot H3,the screw being threaded into disc H5. The clips H1 support mercuryswitches I and I 2| Rotation of the shaft I04 causes tilting of themercury switches I20 and I2I. Stops I22 are secured to the disc H 5 byscrews or otherwise and cooperate with finger I23 suitably secured tothe frame plate 21. The finger I23 serves to cooperate with stop I22 tolimit the rotation of disc H5 and also serves as an indicator incooperation with a mark on the disc II 5 to show that position in whichthe mercury switches are both out of contact or in neutral position. Inthe neutral positions the mercury switches I 23 and III may both be outof contact making position, or may both be in contact making position;however. when the disc H5 is rotated to an oil. normal position, oneonly of the switches I23 and I2I makes contact. Suitable electricalleads I24 extend-from the mercury switches.

Since rotation of the spirally grooved shaft'lu sition ofthe shaft I04and therefore corresponds to a certain definite lateral position of thestep table 23; Thus the neutral for the instrument is determined. Inorder to adapt the instrument I to a particular installation, adjustmentof the neutral for the instrument is desirable. Such ad- 'justment maybe efifected "by manipulation of thumb screw I25 pivoted upon a studfixed in the side plate 21. Thumb screw I25 carries spur gear I23 whichmeshes with spur gear H2.- Rotation of the spur gear I26 effectsrotation of the spiral shaft I04 and thereby positions the step table 23laterally; By holding the'disc I25 against'rotation while manipulatingthe thumb screw I25. the spring drive between thespur gear "II3"'and thedisc 5 allowing-for slippage, the" position which the step table 23occupies when'the' instrument is in neutral, may be adjusted.

Thus'the' operation of'th'e steptable a g uging the position c t-thepointer 22 and consequent- 1y the operationof the mo'tor'I I I ',j-'causes tilting of themer'cury switches I 20 and-I2 I as to makeaconta'ct through-one orth'e 'other of the mercury switches whichcorressandsteueparturaup' scale -and down-scale oftlie' table'i23 fromits neutral position." Thus a: controlactionis providedwhich'persist's'so long as thtable'23 isf-oif neutrah'an'd 'pointer22 concedsto bccupy'an of! "normal p s r nqn mz i 'a' vi ii'e 't e m asuredcondition from schedule.

The sequenceof operation of the instrument illustrated in Figures 41o 9;is asfollows:

Beginningwith the position of the parts shown in Figures 6, 7, 8, and 9,where cam follower 43 has just passed from a high point to a low"pointoi cam 43 thereby causing lowering of depressor bar 33 to clamp topointer 22, and where the cam follower 58 rides upon a high point of cam53 just prior to movement 'to the low point -oi the cam, thereby holdingthe step table 23 in lowermost position, and where cam follower 13 ridesupon a high point of the cam 59 just prior to falling to a low point ofthat cam and acts through crank 13 to hold selector levers 31, 53, and69 out of engagement with finger 63 andto leave the rock lever 39 freeto rotate against its of that cam, the follower 13 remaining on a highpoint of the cam 59."v The movement'ot the. cam follower 53 results inlifting-the steptable 23 into contact with pointer 22 and the consequentsetting of selector finger into a position which corresponds to theelevation of the step table 23. The depressorbar 33 remains in depressedposition clamping the pointer while the step table engages it. Furtherrotation of the cam 53 allows the cam follower 13 to drop from a highpoint to a low point of the cam thus permitting crank 13 to swing andrelease selector levers 51, 33, and 93 so that they may engage lllatches the hook 95 on tongue 94. The pointer domains clampedand-thestep table remains in engagement with the pointer-rduringtheoperations consequent upon :thedrop on the cam i01- lowcr.:'llirom:ahigh pdintto'a low po'intof the cam ILJMrther operation of the motor 5!and consequent rotation of camsv 44 and 59, causes, by action-o1camiollowe'r 58 andcam 59, the

fl! ,uponcthecam; -58, slowly moves 'lthe J8 ,anddrawsrby, means 10:,hook 96;; the JOCK lever s. to.- he, :l f ,-a .-s wn in Fi 3.1. a ;A

the-rock lever 8311s movedto the left,..the pins a. urge contacts-86intoseng gcment'with the e -one i-th tco tacts. .aztt epointmt ;ti' avtel. of the contact 86 at-.whichiit engages with .the contact,8&beingfletermined bythe stance to which the selectorrlever in questionhas been mqv qnwars cn ia 1 t rn isrdetermin d' by s a ed fl stiont firhe ter; re a- "and hiakecont bf the neutral i s tepdable, 23;;{I'hemove- 1& thelett a es-int at a i Pin 3 .9 'wil tc ih h? fien s-arms. h ped e thee-i nov ens of lthe cranl; J8.

. -alwer monste engih hm: e ch, 1 .8 1? 1th ne ot the contacts fl clh'.l ieriei q tes-ex; Lt'ent ,1 "c m n -i s l ctd l sra i mastic-e whichin eoi-rs o dsw and Inlay be in pre- .cise. accordance with thedeflection oi the pointer 22 relative tol'jthetablefi, The contactbetween contactimeriibersifl and contact Q6. may be -utieifect. anysuitable control action and acts through1-auxiliary circuits to 'set thereversible motor. ill in operation to adjust the step table so that itsneutral position will correspondto the last gauged position or range 01position 015 "the pointer, and at the same time, the mercuryswitchesflland ,IZI will be rotated into for out or contact makingpositionQThecontacts made by the mercury switches may be utilized toeif'e'ct suitable control action. "The continued rotation of the cams bymotor rotates the crank 18 to draw the selector levers 5], B8, and 69out of engagement with theselector finger it, which, when ire ed isurged by the spring 5l1'into a position limited by stop}; 4 The camfollower 'li 'the'nlpassesover thehlgh point of the cam 14andthe'tlepressor bar is lowered to clamp the pointer again'and thecycle of operations is reposted sta ith thestep table ata new datumposition:

*r fq l "1 ntovid q lw i mi variations in the measured l condition, mayact to eiiecta controijact'ion which is in precise accordance''with;,the 'rateot change of condition and with the direction of changeof the measured condition, and also acts to effect a control action solong as a measured condition on schedule,'"the"direction 01 the'lastmentioned control action being in accordance with the direction ofdeviation of the measured condition from schedule.

'1heparticular-mechanis m described for eiicctini the above outlinedcontrol actions" is of 'eirclcctor finger 66. The movement oi the crank.the general type shown in different forms in the prior patents of BeanNo. 1,825,932, granted 0c- "tober 6; 193l,and' Brown No. 1,826,896,granted October- 13, 1931': It maybe varie'din'ma'nybf its details and'ma'y be essentially difierentin its mode of. operation. Thecontrol-instrumenfidcscribed is of the millivoltmetertypey that "ifsfaninstrument in which" the deflection ota-"pointer is in accordancewith--;the'- variations or a" dressuredcondition.- Instruments of v thepotentiometer type which operate upon the principle'i of balancing asystennof force's sci-as t'o bbtain a f null point; may also heemployed" for eiie'cting ;.such; controlia'ctions as obtained'by'thecofitrol instrument herein abovede'sc'i'ibedF Other 'forms 1 ofinstruments 5 whichlactto nieasure 'a huaiitity sand-variations of thequantity," -iin d which' flect l control :actions' in accordancewithfthe' rate' or change of. the' measured quam'tityf the dii'ection ofchange of "the measured quantity' which-act to.provideacompensatingcontrol so long as the a correct direction, are well knowninthe art and .may be employed for the .purposes'ioi this invention.vThe invention isnot limited to aparticular retype -01control-instrumentemployed:

=measured'quantity remains ofischedule and in ,Ihe liquid levelgaugeiorrmeasuringithe level 1 of. liquid in the dephlegmatorutower or i'inittlie reflux leg -oi- ,the .dephlegmator: toweri isdillilS- .t rated-in l ig. '10. .The diiferentiaiz-headzoi pres- .sure isconducted-through"conduitsfi21 and-1128 Yention chambers l;1cf;.conventionalihonstruc- ,',tion, and; ,through oonduits .l 3l..and:.;l llst'osithe -,high and low pressure "sides of -;a. :manometer I33. manometer is. provided within; lowzzpressure high pressure leg: J,in -,the .torm -of= .a pipe fitting threaded into a passage inmhe. baseof, the manometer, theJow andshiglnpressui'e legs being connected bypassage (3G,; JI'he mathrough a condenser i29wand throughisurgeprenorneter chambers containmercu land the liquid 1:

transmitting the pressure to thez manometeris in direct contact withthemercurye'; Qhanges in liquid level within the dephlegmator tower resultin changes in level of .the mercury .within-;the

manometer and fioatjlfl riding uponjhe, surface ofthe mercury/moveswithflhemercury. Float I31 carries armature i38- moving in, tube {33surrounded by induc'tance'brldge coils I40 which are electricallyconnected by leads, Ml with a receiving inductancebridge coil 2 and witha source of alternating current bypower lines 3. Movemen ts'of thearmaturewithin the inductance bridge coils Hllcause movements of'asimilar armature I within the receiving inductance bridge calls (42, Thearmature i is connected byflink H5 throughleveri pivoted fatlll]ancihaving an entension' 1 58 which cont cts with ts mecca na pj 15o.fpivotc'd m thefran' e um;instmmepeigaspring urges arm] as againstextension as; Tlic'shaft'fiflhas 0 which c operates such-as is shown'inFi llmay be anism shown in Fig;

proportionallyrcontrollins :two burner 1 two suchinletssor respectively-ioined "proper through a screw -of lever I80- operates oneor the steamto :a single tbej-supplyrof fuelland iinodified" wane .411 rand lllfforFigures4to9,

in order to actuate the with valves terr regulating the-supply of forregulating the supply pump, a suitable motor driven valve u n fuel.to-the and-- mechanism The motor driven valve wheel I58, pinion I I 69,-gear, IGII, gear I82, fixed to-shaft I63 which carries ec-I centric'pinfects throughxthej-reduction gearing, the rota-' tion ofeccentric.pin.I6l.- Link fiIii is connected to eccentric pin I64and-atits other end i'sjcon I81 and-lever I68 by pin 1 Lever IE8 ispivoted on pin I10 and Joined by pin III to links I12 and I13, Links I12and Sure to cranks; I14 and "II! by: pins I" so that motion of thelever. It} moves the cranks Ill and hand valves Ill and; I18respectivelyrto adjust the vaiveopenins'si The, cranks Ill and by whicheme: tion'between the cranks I14 and theiril' l e tivo. valve-membersmay y pinnedto lever I80 mounted for rotation at I 8i upon the limitswitch box I82.-

extremity. I81 otherflimiti switch I or fltl'when'the valves III and I18have moved to limit of adjustment desired-imeitherdirection.=Suitablefset screws I88 'are provided foradiustingthe limit-switches.

11 with its two c nduits II andlt-is of knowntvpe ,beused without changein the supply fuel to inlets for the furnace I, if the latter can beused in proporsupply. of oil and atom burner inlet for the furto. pr prtionally control combustion air to the the motor I of and control.valves and: form and may 'tionally controlling the be used.

example }'th valve I18, and by omission-inf the corresponding parts In,

dfiand "9. may housed to control the steam toithe pumpt ifi of Fig. 1,-and in such ujflzl lstfll will correspond minutiae-21:01am. 1 and 2..Themeasurins instrumentstogether with the inFig. 1 of the'drawings.

different combinations in,

regulators, as shown may be 1.in order'toeifect the desired controlactions. 111g.

-2 shows. a suitable circuit rliagramjby which one of control actions,which particular combination takes inconsiderationfthe interrelationbetween- =the' variable conditions,

lac:

maybe effected; As'has already. been indicated the meter' instrument ofpyrometer it maybe musm m 1 m tc iwmm ter' II differs-from thatof'pyronieter io'mere'ly in the omission of the low vvalue mercuryswitch mete'rof the liquid-level con-' trailer 28 may be identical withthe meter shown the previously which the pointer III of g.ge'renoc'letter-ll as wellas immune: is-fgiven its movement. For-con in betweenof steam to the.hot' oilj1 v p f f show 'lii l igsi me p o ed). aim-1:1; has motor fi l-mounted inthe base I55 and operl; atlns through-shaftI756, drive I51. worm pinion ;I8I,'= and I; Rotation-ofthe motor IN ef-0! fuel to the I15 may be joined tothejyalve p nacepyrometer controller2. ort'bf-supe'rviso' rycontrol over the fuel feed be adjusted.linkiitl. .-.is' v me! throw of the The motor control valve mecli-"identical wan-incitin "iwith hizhand low 'f'bOhD and! indicate Fig. 2,separate reference symbols are given in Fig.2 toithe different metercontacts, motors and mercury switches corresponding respectively Qto.the contacts. and 86, motors SI and -'III, zandmercury switches I20 andIZI ofzthe meter m'eavan eforfa more detailed description of controlsystem shown in Fig.2 it may be advantageous to note thatthemotor IIIemployed tor t'e feed'fof oil-from thede'phlegmator 9 .to the tubes 2 ofthe'oii -heater iscontrolled exclusively by the oil level controller ilwhich exerts two controlactions' on "that-motor, one ofsaid actionsbeing-a stabiliaing' action responsive to trend or changefin oil-"level:inthe dephlegmator and to prevent'such a change, while the second actionis acompensating action responsive to oil level tendin tomaintainttheoil level in thedephlegmator at a predetermined normal.operation of the motor 2 III of .2 'whichregulates the supply heater 1,and hence the heating eflectof' the latter'is-subject tocontrol-by eachofthethree'ci'nitrollers I8, I8 and 20; The lur I8 normally exercisesand tends to prevent-departure inv the rate -of I feedfromf'standardfrate 'whichgmay bel sometimes constant and sometimesvariable, and which i determined 'by. the actions of the oil- 'level"and transfer-f temperature controllers 20 and I8.""The,fm'nacetemperaturecontroller II reg111ates'-the.-fuel1 fe ed;in response to thefur-. v

*and the oil level controller 20 are combined under some, conditions,and are exerted-individuaily and alone under other conditions. andinclude-actions or control effectsseparately responsive to trend andstatus. The dominant con-i trol of the fuel supply to'the furnace iseffected by the transfer line temperature controller. The controlactions regulating. the oil .feed to the still and the'fuel feed to thefurnace, not only stop the motors IIB and 212, and start them intooperation inone direction or the other under certain conditions, butalso cause each motor to operate at-difierent speeds under certaindifferent conditions. The speed variations of the motors are effected bymeans of resistors 241 and 351, which are associated with the energizingcircuits of motors 2 I0 and 212, respectively in different ways underdifferent conditions making -niotor operations at different speedsdesirable;

In Fig. 2-the symbols F,-B and R adiacent certain contacts and relaysindicate fallin stationary or stopped, and rising trends. The referencesymbols H and L adjacent certain switch- Yes and relays indicate thatsuch switches are closed and relays are energized in accordance status.The reference symthat the oil-and the fuel feeds are decreased and-increased respectively, onthe energizati of.the motorfleld windingsalongside which theaaid symbols D and I are The motor SI of each of thethree in Fig; 2 is designated by the refby an individual referfence'symbol. Thefeamresof the control sysf-

